Normal hair can be so fine, limp, and lacking in body that the hair does not hold a hair set well. Furthermore, hair can lose body and be weakened as a result of being subjected to chemically active hair treatments, such as permanent waves and tints. Additionally, hair can be weakened even further by other contributing factors, such as bleaching by the sun or chlorinated swimming pool water.
The condition and appearance of hair can be improved by applying a composition that conditions the hair and helps maintain the hair in a predetermined configuration, or hairstyle. Hair setting and conditioning can be achieved by applying such a composition to wet hair, fixing the hair by drying, then combing to give finishing touches and provide the desired hairstyle. Similarly, after applying the composition to the hair, the wet hair can be set by using any of a variety of rollers or curlers to mechanically fix the hair in a predetermined configuration before drying. In either case, the wet hair is dried, either by ambient air drying, electric drying, or hot air, i.e., blow, drying, to set the hair.
The inherent problem encountered in hair setting is the natural tendency of hair to return to its natural shape. For example, set hair returns to its natural shape almost immediately if moistened. Likewise, high humidity conditions accelerate the tendency of hair to return to its natural shape. Therefore, intensive efforts have been directed toward providing a hair set with sufficient holding power to maintain the desired hairstyle until at least the next shampoo, and, accordingly, giving the hair set a degree of permanency.
As indicated by the natural tendency of hair to return to its natural shape, hair is an elastic structure. As a result, the slight deformations in hair structure resulting from setting the hair are completely reversible. However, the rate of return of hair to its natural shape is dependent upon the method used to deform, or set, the hair. Hair sets performed with wet strands of hair being rolled tightly, either in curls around the finger or on curlers, followed by drying the hair and unrolling the curlers after drying, corresponds to the release of the hair from a deformation-causing load. The deformation, or set, obtained can last for several days, but the hair set is not retained if the hair is wetted.
Investigators have sought to delay the combined action of natural forces and moisture that cause hair to return to its original state by applying compositions containing naturally occurring or synthetic polymers that assist the hair in retaining the desired hairstyle configuration. When applied to hair from aqueous or aqueous/alcoholic solutions, gels, or mousses, the polymers form a film on the hair, after drying, to help maintain the hair in the desired hair set configuration. The polymeric film promotes cohesion and gives stability to the hair set, and also acts as a moisture barrier. The principal objective of a hair styling composition, therefore, is to cover the styled hair with an invisible polymeric film that gives the styled hair a degree of rigidity, protects the hairstyle against wind and humidity, retains the hairstyle, and imparts a good feel and conditioning to the styled hair.
One type of hair styling composition is a hair spray product. Hair spray products are applied to wet and/or dry hair and contain a polymer, or polymer mixture, that remains fixed on the previously styled hair and effects the hair in various ways. For example, a "mechanical" effect is exerted on each individual hair. The film-forming polymers are used to provide a flexible sheath of polymeric film on the shaped hair after drying, and, therefore, for mechanical reasons, retard the return of each individual hair to its natural shape. In addition, the polymeric film provides an overall stiffening of the hair. The hair behaves as if the individual hair strands are welded together, and the final hairstyle has better cohesion, therefore, resisting the natural forces that return the hair to its natural shape. Finally, the polymeric film protects the hair from humidity. The ability of the polymeric film to attract and absorb water preferably is minimal, such that the polymeric film retards moisture uptake by hair and retards the return of the hair to its natural state.
Hair styling gels are another type of hair styling composition. Hair styling gels are applied to wet or damp hair prior to configuring the hair in a predetermined configuration. Hair styling gels are applied by rubbing the gel onto the hair manually. The treated hair then is dried and set in a desired configuration, such as with a blow dryer.
The general principles of hair styling and setting are thoroughly discussed by C. Zviak, in The Science of Hair Care, Marcel Dekker, pp. 149-181 (1986). Zviak reviews both the polymers used in hair styling products and the formulation principles used to produce a hair styling composition that provides such beneficial hair set properties as improved hairstyle retention, easy application and combing, quick drying and nonstickiness, good hair body and bounce, increased hair volume and gloss, and hydrophobicity. It is evident that in the formulation of any end-use hair styling product, some of these benefits must be sacrificed to some degree to achieve a competing benefit. Therefore, the formulation of hair styling compositions has proved difficult.
To overcome some of the inherent disadvantages of the polymers used to set and style hair, and to minimize the drawbacks of a particular polymer used in the formulation, hair styling compositions are available in diversified forms. For example, hair styling compositions are available as plasticizing lotions, plasticizing gels, aerosol foams, all-purpose lotions, hair sprays, holding lotions, conditioners, and shampoos.
Nonionic, cationic, and anionic polymers have been used in hair styling compositions, with the anionic polymers providing the best hair set results. However, anionic polymers also have disadvantages, such as high water solubility, and, therefore, low hydrophobicity; and low substantivity on hair fibers, therefore, generating a crust and flaking due to easy elimination from the hair by combing and brushing. As a result, investigators have continued to search for compounds and compositions that provide the benefits of improved durability and feel of the hair set, while conditioning the hair.
The use of resins, or polymers, in hair styling compositions is well known, as summarized in Grollier et al. U.S. Pat. No. 4,445,521. The resins typically used in hair styling compositions are linear vinyl (e.g., an alkyl vinyl ether) or acrylic (e.g., an alkyl acrylate) polymers prepared by copolymerizing two or more monomers in a free radical polymerization reaction. The vinyl and acrylic-based resins often are used in relatively high concentrations in a hair styling composition to fix the hair in a particular configuration and to provide good hair set retention. However, at high concentrations, the vinyl and acrylic-based resins exhibit disadvantages that adversely affect the hair, such poor combing, poor feel, and excessive stiffness, crust, and flaking.
The vinyl and acrylic-based hair fixative resins conventionally used in hair styling compositions were designed for use in anhydrous alcoholic hair spray compositions. The resins, therefore, had excellent compatibility with, and solubility in, alcohols (e.g., ethanol) used in pump spray compositions and hydrocarbons used as propellants in aerosol compositions. However, due to environmental and toxicological concerns, government regulations require a decrease in the amount of organic solvents used in hair setting and related compositions. Therefore, the alcohols and the hydrocarbon gases traditionally present in hair setting compositions, and especially hair sprays, are being replaced with water and water-soluble solvents, like dimethyl ether, that pose less harm to the environment. In addition, the traditional hair sprays are being replaced by hair styling gels and mousses.
The solvent changes required by government regulation made the traditional vinyl and acrylic-based resins unsuitable in aqueous hair setting compositions. The presence of water in hair spray compositions increased the viscosity of the composition, thereby making spraying difficult to impossible when traditional resins are used. The relatively high viscosity of the hair spray compositions, therefore, required a reduction in the resin concentration of the composition, which, in turn, results in insufficient hair set retention. The presence of water also increases the tackiness of the resin on the hair, thereby prolonging the drying time of the hair spray on the hair. Water also reduces the hair-wetting ability of the compositions, resulting in beading and flaking of the resin from the hair. In the case of aerosol hair spray products, the combination of water, resin, and propellant gas results in poor delivery and foaming of the composition, large aerosol particle size, and beading of the resin. Similar disadvantages were observed when a traditional hair fixative resin was used in an aqueous hair styling gel.
The disadvantages attributed to traditional vinyl and acrylic resins led investigators to search for new hair fixative resins that overcome the disadvantages associated with the vinyl and acrylic resins. As set forth in European Patent Application 0 619 111, one class of resins is the polyurethanes. However, the hair fixative compositions disclosed in EP 0 619 111 require a base to neutralize, and solubilize, the polyurethane resin. It would be desirable to provide an aqueous hair styling gel that overcomes the disadvantages associated with traditional vinyl and acrylic resins, that imparts good hair style and a natural feel to the hair, that retains the hair set, and that conditions the hair.